This invention relates to the displaying of images in computer graphics, and particularly to a method and apparatus for displaying images suited to display an image formed of an aggregation of fine regions, for example, fine lines such as the human hairs.
The image processing technique using computer graphics has been rapidly developed to enable various different objects to be displayed. The images of objects having anisotropic reflective properties such as the human hair and fur cannot be realistically expressed yet, and thus they are now being investigated in various fields.
A computer algorithm for expressing the anisotropic reflective properties is disclosed in Proc. Graphics Interface '88, pp. 138-145, "FROM WIRE-FRAMES TO FURRY ANIMALS" (Miller). This conventional makes rendering of models of furry animals with short straight fur.
There is another publication of Proceedings of Computer Graphics International '89, pp. 691-700, "New Advances in Computer Graphics" SPRINGER VERLAG, in which the human hair is represented as straight hair. Moreover, a method of processing the surface of an object concerning the two-dimensional representation of a three-dimensional object is disclosed in Japanese Patent Laid-open Gazette JP-A-64-79889.
In the above-given papers, body hairs on a body or head hairs are approximated by an aggregation of short straight hairs, but the actual feeling of the "gloss" which appears when respective lustrous hairs are equal in their direction cannot be represented realistically. Also, the required computing time is too great to be practical.
These problems are assumed to have been caused by the following facts. The development of CG has so far been made chiefly on the anisotropic reflective model itself which has diffused reflection light in macroscopic but aligned reflection light in microscopic, and therefore the investigation has been centered on the development of theoretical expressions and precise or simple analysis of models according to the optical law. In other words, conventional techniques do not effectively specify the color, tone, and brightness for each very small region, or each hair as a unit to be displayed, and does not consider that upon displaying, the outline of an object image should be displayed at high speed for practical purpose even though the display is not a physically strict simulation.